/**
 * OpenKM, Open Document Management System (http://www.openkm.com)
 * Copyright (c) 2006-2012 Paco Avila & Josep Llort
 * 
 * No bytes were intentionally harmed during the development of this application.
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

package com.openkm.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;

/**
 * Adapts a <code>Reader</code> as an <code>InputStream</code>.
 * Adapted from <CODE>StringInputStream</CODE>.
 * 
 */
public class ReaderInputStream extends InputStream {
	
	/** Source Reader */
	private Reader in;
	private String encoding = "UTF-8";
	private byte[] slack;
	private int begin;
	
	/**
	 * Construct a <CODE>ReaderInputStream</CODE> for the specified <CODE>Reader</CODE>.
	 * 
	 * @param reader <CODE>Reader</CODE>. Must not be <code>null</code>.
	 */
	public ReaderInputStream(Reader reader) {
		in = reader;
	}
	
	/**
	 * Construct a <CODE>ReaderInputStream</CODE> for the specified <CODE>Reader</CODE>,
	 * with the specified encoding.
	 * 
	 * @param reader non-null <CODE>Reader</CODE>.
	 * @param encoding non-null <CODE>String</CODE> encoding.
	 */
	public ReaderInputStream(Reader reader, String encoding) {
		this(reader);
		
		if (encoding == null) {
			throw new IllegalArgumentException("encoding must not be null");
		} else {
			this.encoding = encoding;
		}
	}
	
	/**
	 * Reads from the <CODE>Reader</CODE>, returning the same value.
	 * 
	 * @return the value of the next character in the <CODE>Reader</CODE>.
	 * 
	 * @exception IOException if the original <code>Reader</code> fails to be read
	 */
	public synchronized int read() throws IOException {
		if (in == null) {
			throw new IOException("Stream Closed");
		}
		
		byte result;
		
		if (slack != null && begin < slack.length) {
			result = slack[begin];
			
			if (++begin == slack.length) {
				slack = null;
			}
		} else {
			byte[] buf = new byte[1];
			
			if (read(buf, 0, 1) <= 0) {
				result = -1;
			}
			result = buf[0];
		}
		
		if (result < -1) {
			result += 256;
		}
		
		return result;
	}
	
	/**
	 * Reads from the <code>Reader</code> into a byte array
	 * 
	 * @param b the byte array to read into
	 * @param off the offset in the byte array
	 * @param len the length in the byte array to fill
	 * @return the actual number read into the byte array, -1 at the end of the stream
	 * @exception IOException if an error occurs
	 */
	public synchronized int read(byte[] b, int off, int len) throws IOException {
		if (in == null) {
			throw new IOException("Stream Closed");
		}
		
		while (slack == null) {
			char[] buf = new char[len]; // might read too much
			int n = in.read(buf);
			
			if (n == -1) {
				return -1;
			}
			
			if (n > 0) {
				slack = new String(buf, 0, n).getBytes(encoding);
				begin = 0;
			}
		}
		
		if (len > slack.length - begin) {
			len = slack.length - begin;
		}
		
		System.arraycopy(slack, begin, b, off, len);
		
		if ((begin += len) >= slack.length) {
			slack = null;
		}
		
		return len;
	}
	
	/**
	 * Marks the read limit of the StringReader.
	 * 
	 * @param limit the maximum limit of bytes that can be read before the
	 *        mark position becomes invalid
	 */
	public synchronized void mark(final int limit) {
		try {
			in.mark(limit);
		} catch (IOException ioe) {
			throw new RuntimeException(ioe.getMessage());
		}
	}
	
	/**
	 * @return the current number of bytes ready for reading
	 * @exception IOException if an error occurs
	 */
	public synchronized int available() throws IOException {
		if (in == null) {
			throw new IOException("Stream Closed");
		}
		
		if (slack != null) {
			return slack.length - begin;
		}
		
		if (in.ready()) {
			return 1;
		} else {
			return 0;
		}
	}
	
	/**
	 * @return false - mark is not supported
	 */
	public boolean markSupported() {
		return false; // would be imprecise
	}
	
	/**
	 * Resets the StringReader.
	 * 
	 * @exception IOException if the StringReader fails to be reset
	 */
	public synchronized void reset() throws IOException {
		if (in == null) {
			throw new IOException("Stream Closed");
		}
		
		slack = null;
		in.reset();
	}
	
	/**
	 * Closes the StringReader.
	 * 
	 * @exception IOException if the original StringReader fails to be closed
	 */
	public synchronized void close() throws IOException {
		if (in != null) {
			in.close();
			slack = null;
			in = null;
		}
	}
}
